Abstract

Immune-mediated regression of melanocytic neoplasms is thought to be a predominantly lymphocytic host process driven by CD8+ anti-tumoral T-cells, and is the basis for melanoma immunotherapy. We report a 27-year-old woman with no significant past medical history who presented for evaluation of a growing pigmented lesion on the left lateral calf. On exam, a 5mm dark brown papule with surrounding rim of erythema was identified, with clinical suspicion for melanoma. There was no history of trauma to the lesion. A punch biopsy was obtained. H&E stained sections showed a sparse atypical junctional melanocytic proliferation, with empty spaces in the epidermis where melanocytic nests likely occupied, with only a solitary residual nest and a focal area of crowded single melanocytes along a hair follicle highlighted by SOX10 immunostain. In the superficial dermis, there was a mixture of predominantly acute inflammation with prominence of neutrophils and eosinophils. A final diagnosis of a near-completely regressed melanocytic neoplasm with acute inflammation was made. To our knowledge, regression of a melanocytic neoplasm with acute (neutrophilic and eosinophilic) inflammation has not been previously reported. The clinical relevance of this finding is not clear, but raises the possibility of a non-traditional, non-T cell mediated pathway of regression of melanocytic neoplasms.

Financial Disclosure:
No current or relevant financial relationships exist.